1. Field of the Invention
The present invention relates to a method and a device for simulating slip on vehicle test benches in accordance with the equation FR=FA× the coefficient of friction C of a vehicle wheel rolling on a test device such as a test roller or flat belt.
2. Description of the Related Art
In order to test antilock brake systems (ABS) on brakes, traction controllers on drive systems or electronic stability programs for preventing skidding, it is generally known to drive the respectively equipped vehicles over test routes. For this purpose there are slalom courses, circular courses, or oblique planes which can have various underlying surface coverings in different locations and the coefficient of friction can be partially reduced by water when necessary. It is thus possible, for example, to create different frictional conditions on the two sides of a vehicle and to generate slip between the tire and underlying surface on a drive side in a selective fashion. When such courses are driven, the vehicle may be caused to skid in a controlled fashion so that the effectiveness of the respective vehicle systems can be tested. However, such test journeys are dangerous for the driver and cannot be reproduced owing to the changing environmental conditions or the different performances of even the same drivers of different course paths so that these tests can only provide approximations for the further development of affected vehicle safety systems.
On vehicle test benches, for example, roller or flat belt test benches, it is possible to provide different surfaces with different coefficients of friction at the various wheels and water can be introduced between the tire and the test surface in order to reduce the coefficient of friction. For this purpose, the test bench devices must all be made corrosion-proof and complex feed systems and collecting systems for the water have to be provided. In order to change the basic conditions at the various wheels, it is necessary to reconfigure the entire test bench or replace the coatings of the testing surfaces. Another disadvantage is that the method in which the frictional force, which limits the maximum tractive force of a wheel, is changed by changing the coefficient of friction is difficult and cannot be set precisely and in addition only a static testing mode owing to the time delay when the surfaces dry.